These studies will explore the biologic role of the mesangium with respect to the uptake and disposal of macromolecules. This will include an analysis of the role of electrostatic charge of macromolecules such as ferritin and immune complexes made with ferritin and albumin of different isoelectric points. These studies will be correlated with studies of the mononuclear phagocytic system. The afferent and efferent mesangial limbs will be further defined by studies using these probes in experimental renal disease.